Modern semiconductor factories use a variety of automation systems from multiple independent suppliers. As used herein, the terms semiconductor factory and semiconductor fab are synonymous, and are respectively abbreviated as factory and fab. The various independent automation systems include hardware and software that are interfaced to work together to automate the movement of material, data, and control through the fab. Major independent automation systems in the fab may include: MES (Manufacturing Execution System), AMHS (Automated Material Handling System), MCS (Material Control System), station Control for tool connectivity, EFEMs (Equipment Front-End Modules) and loadports for interface between factory tools and the AMHS, material tracking systems like radiofrequency identifier (RFID) and barcode, and associated independent software products that may or may not be used in a factory and may or may not be bundled together to handle functions like fault detection, recipe management, scheduling and dispatch, statistical process control (SPC), and others.
Although the various automation systems are defined to work independently in a particular fab, there is currently no single automation system that aggregates data and control on a fab-wide basis. The result is that the productivity of the entire system, i.e., of the entire fab, may not be optimized even when the independent automation systems are functioning effectively. While the independent automation systems may not directly impact the yield of semiconductor devices per wafer, the independent automation systems do impact overall fab productivity in the areas of cycle time, throughput, WIP (Work-In-Progress) levels, material handling, etc.
When a new fab comes online or when fabrication of a new chip design begins, issues and problems may exist in the fab which adversely affect device, i.e., chip, yield per wafer. Therefore, at the beginning of fab life or at the beginning of a new product fabrication ramp, a major focus of the fab is on improvement in device yield per wafer. As device yield improves, the focus of the fab may turn more toward improvement in fab logistics and productivity. Improvement in fab logistics can be of particular concern with regard to fabrication of larger wafers. For example, fabrication of 300 mm and larger wafers requires more automated transport through the fab, thereby benefiting from improved fab logistics. Also, fabrication of smaller technology node devices having decreased line widths may require more process steps, which in turn requires more automated transport through the fab and increases the complexity of cycle time control in the fab. Therefore, improvement in fab logistics can also benefit fabrication of smaller technology node devices.